Auxiliary control surface for highspeed aircraft



Feb. 8, 1949. s, BENTNALL 2,460,804

AUXILIARY CONTROL SURFACE FOR HIGH SPEED AIRCRAFT Filed May 22, 1944 vINVENTOR 5P5 7M g g FIGS Patented Feb. 8, 1949 AUXILIARY CONTROL SURFACEFoR HIGH:

s-rrnn AIRCRAFT Samuel B. Brentnall, Washington; DLC. Application May22, 1944. Serial No. 536.660"

(cran -13) (Granted under: the act of March: 3, 1883, amended April 30,1928; 370i0. G1 757 i Claims.

The invention described herein maybe manufactured and used by, or forGovernment for governmental purposes, without the paymentto me of anyroyalty'thereon. 1

This invention relates to auxiliary control surfaces for use primarilywith high speeda-ir-craft.

Present experiences with high speedqmilitary aircraft; particularly] thetype having a central cabin enclosure or nacelle arranged-in closeproximity to a pair ofmotor nacelies have tended to show that the areasimmediately adjacent the nacel les'and particularly between the motornacelles and the cabin act in the same manner as Venturitubes and thatinv these areas, as well as the area outsidethe motorznacelles, theairspeed usually exceedsthe speed of the aircraft due to this-Venturiaction. During. dives, when the. velocity of the plane may rise to fromfourto; six hundred miles perhour; the Velocity of air passing. betweenthe: motor nacelles and the central cabin, as well as the air passing onthe outside ofthemotor nacelles may increase, due to the Venturi action;to a point where it approaches, or: even exceeds, the velocity of soundat that altitude.

, Whenever the velocity of the air approaches erconsiderable percentageof the velocity of sound, usually from sixty to seventy percent thereof,there'is a distinct tendency of air upon striking anyobstruction tobreakup into what maybe termed a burbling air stream rather than to followthe airformpath- Since the velocity of sound is a function ofatmospheric temperature these waves tend to form at difierent speeds'atdifferent elevations. At high elevations, where .the speed of soundisconsiderably less than at sea level, burbling would occur atmuch lessairspeed than at sea level. When such waves areformed, the air breaks upinto eddies orburbling.

Such burbling is apt to originate upon any obstruction, such as theedge-oi" a wing, but is most. likely to originate at re-entrant edges,such as at the point of intersection of' the nacelles with the wingsurface, and on flaps or other obstructions which break the continuingof the air stream or they may occur at several such pointssimultaneously.

When theburbling originates at more than one point, the patterns mayoverlap and thus cover wide areas, and in suchcases the tailstructuremay be entirely within the area of one or more of these areas. Shouldthe tail structure of a plane become shrouded in such'an eddy, it wouldimmediately lose its efiectiveness and the plane controllabilitydecreases until such time as the tail emerges from the burblingarea, orthe burbling ceases.

It is an object of the present invention to improve the control of highspeed aircraft.

Another object of the present invention is to provide anauxiliarycontrol for high speed aircraft in. the event that primarycontrol becomes blanketed out. r

Another. object is toneutra-lize thewefic'eot of compressibility: wavesin the air.

A further object is to insure greatersafety in high speed aircraft.

Other objects will become: apparent1from com sideration of thefollowing. specifications; which, when taken in conjunction with theaccompanying. drawings, disclosespreferredforms of the invention.

According to the present invention, a- -supple mental surface isprovided in an arearnot nor? mally affected by turbulentwakawhich-suriaee is adapted to create alift to thevnose of the planeupon loss ofefiectiveness'oi theelevator and restore control ot theplane;

In the drawings; Fig. 1 is a sideelevational View of an airplaneinvolvingthe present invention;

Fig. 2 is a plan view of tha plane shown-in Fig. 1;

Fig. 3is afragmentaryside'elevational viewsof a modification of theinvention;..

Fig. 4 is a fragmentary plan-view of f'the modification shown inFig; 3;and

Fig. 5 is a fragmentary plan view of-a: second modification;

Referring to the drawingsathe-aircraft is shown as being a monoplane'having: wings l0; a-;central cabin nacelle l I, a .pair of. motornacelles I4-l4, housing motors (not shown) which drive propellersl5-l5;- As-shown, the motor nac'elles carry the tail structuregenerallydesignatedaI1 The tail structure l'l includesverticalfins': 18-l 8 l which mount rudders'a l 94-! 9; and a stabilizer Zlimounting anelevator 21.1 The elevator 2| has a trim tab 22 'mOlJHtEdTthEIBOI'LIThe: cabin nacelle l l extends in front. ofthe wings l0. andthepropellers l5; and has mounted thereon: supplemental wing." surfaces"25: The wing surfaces ZB arepreierabIymade with a high aspect ratio,being substantially the: same as the aspect ratio otthe tailrsurfacersoas to produce a liftcurve of comparable-slope; In. the form:o'fiairplaneshown, the wing surfaces 25 are. mountedcahead-of both thewings t0 and the propellers and are also forward of the center ofgravity of the. airplane: and-"are designed to give a constant uplift onthen'oseofthe airplane; which, duringnormal flight ofthe airplane, maybetrimmed out through the trim tab 22; or neutrally trimmed by means.shown in Fig. 4- and Fig. 5.

In operation, the trim tab 22 balances the efiect ofthe supplementalwing surfaces 25 and normal control of the airplane is maintainedthrough the vertical rudders l9-l9 and the elevator 2|. During highspeed dives, however,

altitude with. the result thatturbu'lent wake from the wing or nacellesmay develop and blanket the tail structure, gradually. reducing theeflect of the tail structureto near zero. When this blanketing occursthe supplemental wing surface, being out of the area of excessively highvelocity, and not subject to turbulent wake from any other surface willexert an upward force suffi cient to-bring the plane out of the dive andrestore control to the tail surfaces as the speed re- 7 duces',-the;trimtab22 at this time'being ineifec-' ject to blanketing by turbulent wakeat transsonic speed, a supplemental wing carried by said nacelle forwardof said main wing structure at a predetermined positive angle adapted toprovide lift to the forward end of said airplane, a trim tab carried on'said tail structure said trim tab normally adjusted to trim out the liftof said structure and saidtrim tab are blanketed.

tive -to counterbalance the upward force of the I auxiliary wing surface25. m V, In'steadof having the auxiliary or supplemental wing surfaces25 of Figs. '1' and 2 entirely fixed,

it may be provided with auxiliary elevators 30, as indicated in Figs. 3and 4, the auxiliary elevators being pivotally mounted'ona fixedor'stabilizing portion 31 of the supplemental wing surface, heretoforegenerally designated 25.

The elevators 30 are arranged to be actuated by a torque tube extendingthrough the cabin enclosure H. The torque tube is actuated, as seeninFig. 3, by means 'ofan arm 32 pivotally connected at its lower end toa push rod 33 which is, in'turn, universally pivotallyconnected as at 35to the control stick 36 of the plane.

Thecontrol stick 3B is suitably supported by means of a fitting 31to'the'end of arock shaft 38. A conventionalpush rod 39 is pivotallyconnected to the lower end of the stick 36 and is adapted to actuate theelevator control mechanism 2| in the usual manner.

The ratio of movement 'ofjthe control stick- 36 to the movementof theauxiliary elevators 30, and hence the relative movement of the auxiliaryelevators to the tail structure, may be varied by suitably positioningthe pivot 35 on the stick 36.. 7

'As seen in Fig. 5, the supplemental 'wing surface 25a may be maderotatable as'a unit and controlled by a mechanism similar to thatdescribed for and 4.

the modification shown in Figs-3 While 'the invention has been describedwith respect. to one particular type of aircraft, it'is obvious that anyhigh speed airplaneof either pusher or'tractor type, having motornacelles'arranged on one or both sides of the fuselagev and in closeproximity thereto, may give" rise to turbulent waves blanketing thecontrolsurfaces in a similar manner to that described" above, so thatthe auxiliary control surfaces, in accordance with this invention, wouldbe applicable to .such

' an aircraft. 1

In the case of a single engined aircraft the possibilty ,of air burbling'or turbulent :Waves seriously affecting the horizontal tail surface is1 more remote. However, should sucha condition arise, the invention isaccordingdy applicable to sucha single engined aircraft to limit theloss v .ofcon-trol under such conditions.

What I claim is: I 1. In an airplane, a main wing structure, a tailblanketed by said structure,"two fuselages parallell'y'spaced apartin'fixed position on said wing and tail structures, a nacelle fixed tosaid wing structure intermediate said fuselages, whereby said tailstructure .issub- "2.;In an airplane, a main wing .structure, a tailstructure, one or more fuselages fixed to saidwing and tail structures,a nacelle fixed to said wing structure whereby said tail structure issubject to 'blanketing by turbulent wake at transsonic speed, asupplemental'w'ing carried by said airplane at fixedpositive lift' angleforward of said main wing structurefa trim tab carried on said' tailstructure, said'trim tab normally ad- J'usted to counterbalance the liftof said supplemental wing, whereby the lift effect of said supplementalWingis automaticallyneutralized at adjusted to a negative angle whichnormally counterbalances the positive lift effect of said supplementarywing butallows said lift effect to become operative automatically whenblanketing of said trim tab takes place.

4. In an airplane having'a main wing structure and having a tailstructure' 'which is subject to blanketing by turbulent wake from themain wing structure at trans-sonic speeds, a supplementary wing of fixedpositive lift angle carried by the airplane out of the zone ofsaidturbulent wake, a trim tab carried by the airplane within the zone ofsaid turbulent wake, said trim tab being adjusted to anangle whichnormally-counterbalances the positive lift'eifect of said supple-'mentary wing, whereby said lift effect becomes automatically operativewhen said trim tab is turbulent wake.

R. BRENTNALL.

7 REFER NCES CITED The following references are of 'r'ora' in the fileof this patent) M UNITED STATES PATE NTS Name 7 i 1 N Date,

FOREIGN PATENTS Country Number" Great Britain Oct. 22, 1931

